TG-interacting factor-induced superoxide production from NADPH oxidase contributes to the migration/invasion of urothelial carcinoma

Urothelial carcinoma (UC) of the bladder is the fourth most common cancer and the ninth leading cause of death from cancer among men in the United States. However, higher recurrence, resistance to therapy, and poor diagnostic/prognostic biomarkers of UC prompt us to identify novel targets to improve the clinical applications. TG-interacting factor (TGIF), a transcriptional corepressor to modulate the TGF-β signaling, is associated with various types of human cancer. In the present study, we found that cellular migration activity, reactive oxygen species production, AKT^S473 phosphorylation, TGIF, and p67^phox expression were higher in invasive T24 cells than in noninvasive RT4 cells. In addition, overexpression of TGIF in RT4 cells enhanced cellular migration/invasion ability; it involved NADPH oxidase 2 (Nox2)/p67^phox complex activation, reactive oxygen species production, and AKT^S473 phosphorylation. In contrast, the migration/invasion ability of T24 cells was suppressed by the knockdown of TGIF or p67^phox, respectively. Overexpression of AKT1 could increase cellular superoxide production and invasion. Moreover, by using the PI3K/AKT inhibitor wortmannin or shRNA of AKT1, the TGIF-induced Nox activation and superoxide production were significantly inhibited. Accordingly, we suggest that PI3K/AKT signaling mediates TGIF-induced Nox2/p67^phox complex activation and the resultant superoxide production which reinforces the PI3K/AKT signaling to promote the cellular migration/invasion ability of UC.